package com.xinxi11.module.core.utils;

import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.StringTokenizer;
import java.util.TreeMap;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang3.Validate;

import com.google.common.net.HttpHeaders;

public class ServletUtils {
	// -- 常用数值定义 --//
		public static final long ONE_YEAR_SECONDS = 60 * 60 * 24 * 365;

		/**
		 * 设置客户端缓存过期时间 的Header.
		 */
		public static void setExpiresHeader(HttpServletResponse response, long expiresSeconds) {
			// Http 1.0 header, set a fix expires date.
			response.setDateHeader(HttpHeaders.EXPIRES, System.currentTimeMillis() + expiresSeconds * 1000);
			// Http 1.1 header, set a time after now.
			response.setHeader(HttpHeaders.CACHE_CONTROL, "private, max-age=" + expiresSeconds);
		}

		/**
		 * 设置禁止客户端缓存的Header.
		 */
		public static void setNoCacheHeader(HttpServletResponse response) {
			// Http 1.0 header
			response.setDateHeader(HttpHeaders.EXPIRES, 1L);
			response.addHeader(HttpHeaders.PRAGMA, "no-cache");
			// Http 1.1 header
			response.setHeader(HttpHeaders.CACHE_CONTROL, "no-cache, no-store, max-age=0");
		}

		/**
		 * 设置LastModified Header.
		 */
		public static void setLastModifiedHeader(HttpServletResponse response, long lastModifiedDate) {
			response.setDateHeader(HttpHeaders.LAST_MODIFIED, lastModifiedDate);
		}

		/**
		 * 设置Etag Header.
		 */
		public static void setEtag(HttpServletResponse response, String etag) {
			response.setHeader(HttpHeaders.ETAG, etag);
		}

		/**
		 * 根据浏览器If-Modified-Since Header, 计算文件是否已被修改.
		 * 
		 * 如果无修改, checkIfModify返回false ,设置304 not modify status.
		 * 
		 * @param lastModified 内容的最后修改时间.
		 */
		public static boolean checkIfModifiedSince(HttpServletRequest request, HttpServletResponse response,
				long lastModified) {
			long ifModifiedSince = request.getDateHeader(HttpHeaders.IF_MODIFIED_SINCE);
			if ((ifModifiedSince != -1) && (lastModified < ifModifiedSince + 1000)) {
				response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
				return false;
			}
			return true;
		}

		/**
		 * 根据浏览器 If-None-Match Header, 计算Etag是否已无效.
		 * 
		 * 如果Etag有效, checkIfNoneMatch返回false, 设置304 not modify status.
		 * 
		 * @param etag 内容的ETag.
		 */
		public static boolean checkIfNoneMatchEtag(HttpServletRequest request, HttpServletResponse response, String etag) {
			String headerValue = request.getHeader(HttpHeaders.IF_NONE_MATCH);
			if (headerValue != null) {
				boolean conditionSatisfied = false;
				if (!"*".equals(headerValue)) {
					StringTokenizer commaTokenizer = new StringTokenizer(headerValue, ",");

					while (!conditionSatisfied && commaTokenizer.hasMoreTokens()) {
						String currentToken = commaTokenizer.nextToken();
						if (currentToken.trim().equals(etag)) {
							conditionSatisfied = true;
						}
					}
				} else {
					conditionSatisfied = true;
				}

				if (conditionSatisfied) {
					response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
					response.setHeader(HttpHeaders.ETAG, etag);
					return false;
				}
			}
			return true;
		}

		/**
		 * 设置让浏览器弹出下载对话框的Header.
		 * 
		 * @param fileName 下载后的文件名.
		 */
		public static void setFileDownloadHeader(HttpServletResponse response, String fileName) {
			try {
				// 中文文件名支持
				String encodedfileName = new String(fileName.getBytes(), "ISO8859-1");
				response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + encodedfileName + "\"");
			} catch (UnsupportedEncodingException e) {
			}
		}

		/**
		 * 取得带相同前缀的Request Parameters, copy from spring WebUtils.
		 * 
		 * 返回的结果的Parameter名已去除前缀.
		 */
		public static Map<String, Object> getParametersStartingWith(ServletRequest request, String prefix) {
			Validate.notNull(request, "Request must not be null");
			Enumeration paramNames = request.getParameterNames();
			Map<String, Object> params = new TreeMap<String, Object>();
			if (prefix == null) {
				prefix = "";
			}
			while (paramNames != null && paramNames.hasMoreElements()) {
				String paramName = (String) paramNames.nextElement();
				if ("".equals(prefix) || paramName.startsWith(prefix)) {
					String unprefixed = paramName.substring(prefix.length());
					String[] values = request.getParameterValues(paramName);
					if (values == null || values.length == 0) {
						// Do nothing, no values found at all.
					} else if (values.length > 1) {
						params.put(unprefixed, values);
					} else {
						params.put(unprefixed, values[0]);
					}
				}
			}
			return params;
		}

		/**
		 * 组合Parameters生成Query String的Parameter部分, 并在paramter name上加上prefix.
		 * 
		 * @see #getParametersStartingWith
		 */
		public static String encodeParameterStringWithPrefix(Map<String, Object> params, String prefix) {
			if (params == null || params.size() == 0) {
				return "";
			}

			if (prefix == null) {
				prefix = "";
			}

			StringBuilder queryStringBuilder = new StringBuilder();
			Iterator<Entry<String, Object>> it = params.entrySet().iterator();
			while (it.hasNext()) {
				Entry<String, Object> entry = it.next();
				queryStringBuilder.append(prefix).append(entry.getKey()).append('=').append(entry.getValue());
				if (it.hasNext()) {
					queryStringBuilder.append('&');
				}
			}
			return queryStringBuilder.toString();
		}

		/**
		 * 客户端对Http Basic验证的 Header进行编码.
		 */
		public static String encodeHttpBasic(String userName, String password) {
			String encode = userName + ":" + password;
			return "Basic " + EncodeUtils.encodeBase64(encode.getBytes());
		}
}
